Apparatus for improving the tensile properties of wire



Aug. 20, 1968 Filed Sept. 21, 1965 J. M FA RLANE APPARATUS FOR IMPROVINGTHE TENSILE PROPERTIES OF WIRE Fig.

5 Sheets-Sheet 1 HUVEUT'OR.

TANES Nc. FAR LANE Agent Aug. 20, 1968 J. MCFARLANE 3,398,258

APPARATUS FOR IMPROVING THE TENSILE PROPERTIES OF WIRE Filed Sept. 21,1965 5 Sheets-Sheet 2 INVENTOR.

.TA MES He. FARLANE 1nd 'K- Agent J. M FARLANE Aug. 20, 1968 APPARATUSFOR IMPROVING THE TENSILE PROPERTIES OF WIRE Filed Sept. 21, 1965 5Sheets-Sheet 5 LIJIJI [IIIl/EN'T'OR. James m Fnnume and KM Aug. 20, 1968J. MCFARLANE APPARATUS FOR IMPROVING THE TENSILE PROPERTIES OF WIREFiled Sept. 21, 1965 5 Sheets-Sheet 4 Kw-KM Aug. 20, 1968 Y J. M FARLANE3,398,25g

APPARATUS FOR IMPROVING THE TENSILE PROPERTIES OF WIRE Filed Sept. 21,1965 5 Sheets-Sheet 5 luvs-T RI TANES MC FARLAME KJ-KLLM Agent UnitedStates Patent 3,398,258 APPARATUS FOR IMPROVING THE TENSILE PROPERTIESOF WIRE James McFarlane, Penn, Wolverhampton, England, assignor toG.K.N. Somerset Wire Limited, London, England, a British company FiledSept. 21, 1965, Ser. No. 488,929 9 Claims. (Cl. 219-155) This inventionrelates to apparatus for effecting permanent elongation of wire made inmartensitic forming steel, so as to improve the creep resistance of thewire under tensile loading, thereby enabling the wire to be especiallyeifective as prestressing element in concrete structures as well as atensile element in other structures demanding a high tensile stress,e.g. suspension bridge cables. By the expression martensitic formingsteel, as used herein, is meant steel that transforms into martensitewhen cooled rapidly from a martensitic forming temperature range. Thewire, the creep resistance of which is improved by apparatus accordingto the present invention, may be in the form of a single length of wireor alternatively it may be in the form of a plurality of side by sidelengths of wire, eg as wire in the form of helically wound strand orrope.

The invention is concerned with apparatus for effecting permanentelongation of martensitic forming steel wire and which apparatus is ofthe kind (herein called the kind specified), comprising one or morerotary members around which the wire is passed in such a manner as toapply tension to the wire, means for supplying a heating current to andalong a predetermined length of the wire which is under tension, so asto heat such length to a temperature such that at the tension applied tothe wire permanent elongation thereof is effected, said heating currentsupply means comprising at least one rotary member onto or off which thewire under tension passes, which rotary member is provided with acommutator segment and an associated current supply brush connected to aheating supply circuit.

For convenience in description the said length of wire will be hereinreferred to as the length of wire to be heated even though in respect ofthe length of wire passing onto a rotary member, at least some heatinghas already taken place.

Hitherto difliculty has been encountered in the operation of apparatusof the kind specified by reason of sparking and in some cases evenarcing at the positions where the length of wire to be heated passes outof and into contactwith the periphery of the rotary members thereindescribed.

This difiiculty arises from the fact that hitherto in apparatus of thekind specified, the heating current has been supplied to the rotarymembers referred to in such a manner as to be free to pass to theperiphery of these members at the positions where the wire is passingoff and onto the members, and by reason of the natural tendency for theheating current to take the shortest possible path, an appreciableportion of the entire current is supplied to the length of wire to beheated at the position where the wire is moving into or out of contactwith the rotary member concerned as it passes onto or off suchparticular member.

The resultant sparking and arcing is liable to be of considerablemagnitude, because to obtain the required heating temperature to ensurepermanent elongation of the wire a relatively high heating currentdensity must be employed, which hitherto has been of the order of 900amperes, and for future developments, currents as high as 4000 to 5000amperes are envisaged.

This parking or arcing is especially liable to happen where the wire isin the form of helically wound strand ice or rope so as to be ofnon-uniform configuration peripherally.

Such sparking or arcing can also occur as a result of shunt how ofcurrent between the wire and the adjacent periphery of the rotary memberso as to flow circumferentially therein and then back from the rotarymember to the wire even where the latter is in pressure engagement withthe rotary member. This is because the crosssection of the wire engagingperiphery of the rotary member is relatively large. This sh-unt flow isespecially liable to produce sparking or arcing in the case of strand orrope, in that it occurs between circumferentially spaced positions atwhich the helical windings of the strand or rope engage the rotarymembers locally.

This sparking or arcing in addition to being liable to cause damage tothe surface of the wire, which is undesirable irrespective of theintended use of the wire, is particularly serious in the case of hightensile wire formed of steel of the class specified, because thesparking or arcing, locally and momentarily, raises the temperature ofthe steel to such a high value as to produce martensite by subsequentimmediate rapid conductive cooling to the neighbouring mass of steelwhich has not been so locally heated. As a result, the wire is locallybrittle and its required tensile properties are seriously impaired.

The present invention has for its object the provision of an improvedarrangement which enables the foregoing difiiculties to be avoided.

With the foregoing object in view, the present invention providesapparatus of the kind specified, which is characterised in that eachrotary member which is provided with a commutator segment, has its wireengaging periphery formed as a set of commutator segments spaced aroundthe circumference of the associated rotary member, with adjacentsegments insulated from one another, and the associated current supplybrush comprises at least one current carrying brush, each arranged tomake contact with the commutator segments, at a circumferential positionsuch that each segment which is in electrical contact with a currentcarrying brush, is out of electrical contact with that portion of thewire engaging periphery of the rotary member onto or off which thelength of wire to be heated momentarily passes, the arrangement beingsuch that the current flows between each brush and only that commutatorsegment or segments which is electrically connected to a part of theperiphery of the rotary member with which the wire is momentarily inpressure engagement, and each commutator segment being of such a smallcircumferential length as to provide in parallel with the length of wirein engagement with its periphery a shunt resistance of value greatenough as to preclude sparking or arcing by shunt current how ofmagnitude great enough to result in local formation of martensite.

In practice it is found that shunt current flow of magnitude greatenough to result in martensite formation in the particular wireprocessed may be avoided by making the circumferential length of eachsegment at its Wire engaging periphery not greater than six times thediameter of the wire for which the apparatus is designed.

With the present invention, the heating current is prevented fromflowing from the Wire to the periphery of the rotary member adjacent tothe point of entry or exit of the wire from said rotary member, i.e. theposition at which the wire passes onto or off the periphery of themember. This is because the commutator segments are connected only tothat portion of the wire engaging periphery of the rotary member withwhich the wire is already momentarily in pressure contact. Thus thecommutator segments which are momentarily adjacent the point of wireentry or exit are not in contact with the current supply brush orbrushes, and are electrically insulated from the heating currentcircuit. The heating current apart from any shunt current of magnitudesmall enough to be tolerated is accordingly forced to flow along thewire beyond the point of wire entry or exit, so as to pass to or fromthe periphery of the rotary member concerned at a position where thewire as a result of the tension therein, is in pressure engagement withthe rotary member, ie at a position where there is no likelihood of anyarcing or sparking taking place.

The invention is illustrated in the accompanying drawings wherein:

FIGURE 1 is a side elevation of one form of apparatus embodying theinvention.

FIGURE 2 is a plan view of the apparatus depicted in FIGURE 1.

FIGURE 3 is an end elevation looking in the direction of the arrow 3 inFIGURE 1.

FIGURE 4 is an interrupted sectional view to an enlarged scale on theline 44 of FIGURE 1.

FIGURE 5 is a side elevation to an enlarged scale of part of theconstruction shown in FIGURE 1, showing the arrangement of the currentcarrying brushes.

FIGURE 6 is a sectional view on theline 66 of FIGURE 5, showing to anenlarged scale certain details of one of the current carrying brushes.

FIGURE 7 is a diagrammatic side elevation of the construction shown inFIGURE 1, illustrating the arrangement of the electrical connections tothe current carrying brushes.

FIGURE 8 is a detailed view of part of FIGURE 7, showing more clearlythe arrangement of electric resistance in the current supply leads tothe commutator segment brushes.

Referring firstly to FIGURES 1 to 3 of the drawings, the apparatus thereillustrated comprises a frame 10 on which is supported for rotationabout mutually parallel horizontal axes two rotary members 11, 12, eachin the form of a pulley having a plurality of V section grooves 13. Thetwo members are of the same peripheral diameter and are mechanicallycoupled together so as to rotate in the same direction and at the sameperipheral velocity. For this purpose the two rotary members 11, 12 areprovided at one side thereof with a sprocket wheel 14, the two sprocketwheels being connected by a sprocket chain 15.

The rotary member 11 which is disposed adjacent one end of the frame 10is power rotated from an electric motor 16, which drives the main driveshaft 17 carrying sprocket wheel 18, which is connected through sprocketchain 19 not shown, to sprocket wheel 20 connected to the rotary member11.

At the end of the frame 10 furthest from rotary member 11, so as to beon the side of rotary member 12 furthest from member 11, is a thirdrotary member 21 in the form of a pulley having a single peripheral Vsection groove 22 around which is passed the length of wire to beheated.

The wire 23 which is to be permanently elongated passes first of allaround rotary member 12, then around member 11, then back to member 12then back to member 11 and so on so as to pass successively between members 12 and member 11 around one of the grooves 13 and each of thesemembers in turn, in such a manner as to have an arc of contact with eachgroove of approximately 180". The grooves 13 are formed to ditferentdiameters as shown, eg in FIGURE 4, so that the diameter of the severalgrooves of the members 11 and 12 around which the wire 23 passesincreases progressively in the direction of wire advancement to applyprogressive increase in tension to the wire. In the case, however, ofthe groove 13a of member 11, which is the last but one of the grooves ofprogressively increasing diameter, the wire passes directly from thisgroove 13a along wire path 23a to rotary pulley member 21, and from thelatter along wire path 23b back to that groove 13b of member 11, whichis the last of the succession of grooves which are of progressivelyincreasing diameter in the direction of wire advancement. Thereafter thewire passes successively between members 11 and 12 around grooves 13,some of which are of progressively decreasing diameter in the directionof wire advancement, so as progressively to reduce the tension in thewire passing out of the apparatus, while the final grooves 13 in thedirection of wire advancement are of the same diameter and act as a drawolf capstan for applying suflicient tension as to pull the wire throughthe apparatus. The wire initially passing onto member 12 is fed theretofrom a supply reel not shown through pay off guide 24 and aroundpre-tensioning reel 25 mounted for free rotation about a vertical axis,and being provided with a brake 26, from which reel 25 the wire under acertain initial tension provided by the brake is fed to member 12.

Thus the length of wire to be heated, ie that designated 23a and 23b,passes from groove 13a of rotary member 11 around rotary pulley member21 and back to groove 13b of member 11 without in so doing passingaround member 12, and this is ensured by mounting member 21 for rotationabout an axis which is inclined to the horizontal, as shown in FIG. 3,in such a manner that the portions of the periphery of member 21 ontoand off which wire lengths 23a and 23b pass are situated in verticalplanes, each lying beyond the corresponding end faces of member 12.

For supplying heating current to the length of wire 23a and 23b to beheated, members 11 and 21 are each provided with two sets of currentcarrying brushes; 27, 28 in the case of member 11; and 29, 30 in thecase of member 21.

Each set of brushes 27, 28 are respectively adapted to supply current tothe V section grooves 13a and 13b of rotary member 11, for which purposeeach of these two grooves 13a and 13b is formed in a correspondingcurrent conducting ring 31, 32 respectively, each ring being formed as anumber of commutator segments 33, there being for example in onepreferred arrangement as many as or even segments to each ring, wherethis has a diameter of about 2.3 metres.

In order to prevent undesirably large shunt flow of the heating currentfrom the wire to the commutator segments along the periphery thereofparallel to the length of the wire with consequent risk of martensitebeing formed as above described, it has been found that thecircumferential length of the wire engaging periphery of each commutatorsegment 33 should not exceed six times the diameter of the wire. If thislength is exceeded the area of contact between the wire and the V grooveof each segment 33 becomes so great as to encourage undesirably largeshunt currents.

Where, as is the case with the preferred operation of the apparatus, thewire is in the form of helically wound strand or rope formed of steel ofthe class specified, the periphery of this will engage each of the twosides of V grooves 13a, 13b at circumferentially spaced positionscorresponding to the axially adjacent crests of the wires or strandsrespectively forming the strand or rope to be elongated. Usually suchaxially adjacent crests are spaced by a distance which is just overtwice the diameter of the strand or rope and by making thecircumferential length of each segment 33 not more than four times thestrand or rope diameter it is ensured that the strand or rope is incontact with each side of the V groove at two positions only, therebymaking the shunt current of a mag nitude which in practice will be ofabout of the heating current which is a very small and quite acceptablefigure. If the above ratio figure of circumferential length to strand orrope diameter is reduced to not more than two, each side of the V groovewill be in contact with one crest only per segment, and the shuntcurrent elfect is then eliminated or virtually eliminated, so that thislatter ratio value of segment length to strand or rope diameter is thetheoretical maximum value desired.

The two rings 31, 32 are mounted on adjacent corresponding ends ofrotary member 11 by forming each end adjacent its periphery with a rightangle section groove 34, the axially extending face of which is providedby an annular flange 35. Each of these flanges is formed with acircumferentially extending row of tapped holes 35, through which andthe segments 33 pass bolts 37 to secure the segments in position.

Between each segment 33 and each of the two faces of the angle sectionrecess 34 is a layer of electrical insulating material 38, while similarinsulating material is provided between the bolts 37 and the segments33, so that each of the two rings 32 providing the grooves 13a and 13bare electrically insulated from the main body of the rotary member 11.

The circumferential length of each segment constituting each ring 32 issuch that a small air gap 39 is provided between circumferentiallyadjacent segments. Thus each segment is electrically insulated fromadjacent segments in addition to being so insulated from the member 11.

Each segment 33 presents an outer axially directed fiat brush engagingface 40.

The wire receiving groove 22 of rotary pulley element 21 is provided inan annular ring 32 built up from a number of segments electricallyinsulated from one another and from the main body of the element 21 inlike manner to the rings 32 of rotary member 11, and one of the twoaxially directed end faces 41 of this ring 32 of member 21 is of flatconfiguration, so as to be adapted to engage the associated currentcarrying brushes 29, 30.

The construction and arrangement of each set of current carrying brushesassociated with the rotary members 11 and 21 will now be described.First of all referring to FIGURE 1, it will be seen that the length ofwire 23a advances out of contact with groove 13a of member 11substantially at the peripheral position A, and advances into contactwith groove 22 of member 21 substantially at the peripheral position B.

Similarly, the length of wire 23b which is also heated, leaves groove 22of rotary member 21 substantially at the peripheral position C, andpasses to groove 13b of member 11 substantially at the peripheralposition D. The two positions A and B are made slightly variable in aperipheral sense because the length of wire 23a passes over a tensionmeasuring device consisting of a pulley 42, the wire engaging peripheryof which is shown in FIGURE 1, so that the parts of the wire length 23arespectively approaching a leaving pulley 42 are at a slight inclinationto one another, so that pulley 42 is subjected to a loading proportionalto the tension in this length of wire 23a. The pulley 42 is supportedagainst such loading by some form of measuring device such as anaccurate spring balance, whereby the maximum tension to which the wireis subjected may be observed.

The brushes 27, 28, 29, 30 are circumferentially spaced from the abovementioned positions, A, D, B, C, respectively, by a distance in eachcase greater than the circumferential length of each commutator segment33, so that the particular segment, the groove of which is momentarilyin contact with the wire at positions A, B, C, D is at such time out ofdirect electrical connection with any of the adjacent current carryingbrushes. This ensures that at each position A, B, C, D where the lengthsof wire which are being heated pass into and out of pressure contactwith the sides of the V shaped grooves 13a, 13b and 22 there is nosparking or arcing at all between the surface of the wire and the sidesof the V shaped grooves apart from that resulting from any shunt currenteffect.

Each set of brushes comprises a number of separate brushes 43 eachmounted in a brush holder 44 carried on but electrically insulated froman arcuate shaped mounting bar 45, the opposite ends of which areconnected by brackets 46 to suitable supports on the machine frame 10.Each holder 44 carries an axially extending brush 43 which engages theadjacent end face of the corresponding segmental ring 32.

The ararngement is such that several individual brushes 43 are providedin each set, with circumferentially adjacent brushes spaced apart so asto be out of direct electrical contact with one another, with each brushbeing provided with its supply lead 47 to the current supply bus-bar 48,of which a pair are provided in the case of rotary member 11, one oneach side thereof, and a single bus-bar in the case of rotary member 21.

Each brush 43 has a width measured in a circumferential direction whichdoes not exceed and preferably is less than the circumferential lengthof each commutator segment. Thus each br-ush can never engage more thantwo commutator segments at any one time.

The several brush leads 47 of each set of brushes incorporateresistances 49 of differing electrical resistance such that theindividual brush 46 of each set which is circumferentially nearest topoint A, B, C, D as the case may be is associated with a brush lead 47of greater electrical resistance, the electrical resistance of eachbrush lead 47 decreasing progressively in a circumferential directionfrom the point of wire engagement or disengagement A, B, C, D as thecase may be.

By reason of the foregoing and the fact that each brush can never engagemore than two commutator segments at the same time, the natural tendencyof the heating current to take the shortest path between each set ofbrushes and the length of wire 23a or 23b is taken care of, and bysuitably selecting the value of each brush lead resistance 49 havingregard to the diameter of the wire to be heated and the heating currentselected, it is readily possible to ensure that the current flow betweenthe wire and the periphery of the rotary member is substantially uniformover a portion of the Wire of substantial length corresponding to theoverall circumferential length of those circumferentially adjacentsegments 33 which are simultaneously in contact with the various brushesconstituting each set of brushes. Thus, an undesirably high localcurrent flow between the wire receiving grooves and the adjacent surfaceof the wire with consequent overheating thereof is avoided.

This is of particular importance because the wire Will in practice he ofcircular or substantially circular form in cross-section, and thegrooves 13a, 13b or 22 are made of V form in cross-section in order tominimise slip between the wire and the rotary members, and thus developthe required tension in the length of wire to be heated. Thus, the areaof contact between the grooves and the wire is small. The provision ofthese differential resistances 49 also ensures that each individualbrush will carry the maxim-um current that it is designed to carry,whereby the brushes are utilised in the most economical manner.

As shown in FIGURES 7 and 8, the several bus-bars 48 are connected tosupply leads 50 themselves connected to a current supply transformer,not shown, which may be arranged to provide a heating current of theorder of 50 volts and a magnitude which may be of the order of 4,000 to5,000 am-peres or more, if desired. The particular voltage and currentis dependent on the size, i.e. cross-sectional area of the wire, e.g.strand or rope to be processed.

If desired, for this latter reason, the number of individual brushes inthe two brush sets 28, 30, may be less than those in the brush sets 27,29. This is because the temperature of the advancing length of wire tobe heated necessarily increases progressively in passing from position Ato position D. Thus the mean electrical resistance of the steel Wirewhich increases with increase in temperature is greater for length 23bthan for length 23a. Accordingly, the current passing along length 23bis less than for length 23a. Thus if all of the brushes are to be loadedto the same maximum current density and thus utilised in the mosteconomical and efficient manner, less brushes are required for sets 28,30 than for sets 27, 29. Thus, with twenty brushes at each of theselatter sets there may be only fourteen brushes at sets 28, 30.

If desired, the rotary pulley member 21 need only be provided with asingle set of brushes instead of two sets as shown, in which case theresistance of each lead must be adjusted from -a maximum at either endof the single set of brushes to a minimum at the mid-point.

Preferably, the length of heated wire 23b just before passing onto therotary ember 11 is cooled in the known manner, so as to preventundesirable heating of the rotary members 11, 12, as well as to preventthe wire from assuming a permanent curved configuration corresponding tothe curvature of the members 11, 12, as the wire will tend so to do ifit passed thereon while still hot.

The apparatus operates to effect a controlled permanent elongation ofthe wire, while completely avoiding any arcing or sparking of magnitudeenough to form martensite at positions between the surface of the lengthof Wire which is being heated and the periphery of the associated rotarymembers, 11 and 21 through which the heating current passes.

If desired, the wire may pass in figure of eight fashion between the tworotary members 11, 12, so as thereby to increase the circumferentiallength of each member which is in engagement with the length of wirepassing therearound, in which case it is necessary for the two members11, 12 to be mechanically coupled together in such a manner as to rotatein opposite directions at the same peripheral velocity instead ofrotating in the same direction.

The present invention is not limited to apparatus for improving thetensile properties of wire for structural purposes. Such wire withimproved tensile properties may be used for other purposes where hightensile properties are of especial importance; for example, brakecables, control cables, overhead conductor wire supports.

What I claim then is:

1. Apparatus for effecting permanent elongation of martensitic formingsteel wire, so as to improve the creep resistance thereof, saidapparatus comprising rotary means adapted to apply tension to .a lengthof wire passing over said rotary means in engagement therewith, meansfor supplying a heating current to and along a predetermined length ofthe wire which is under tension, so as to heat such length to atemperature such that at the tension applied to the wire permanentelongation thereof is effected, said heating current supply meanscomprising a rotary member having a wire engaging periphery formed as aset of commutator segments spaced around the circumference of theassociated rotary member, with circumferentially adjacent segmentselectrically insulated from one another, a current supply meansassociated with each set of commutator segments and comprising at leastone current carrying brush, each arranged to make contact with thecommutator segments at a circumferential position such that each segmentwhich is in electrical contact with a current carrying brush, is out ofelectrical contact with that portion of the wire engaging periphery ofthe rotary member onto or off which the length of wire to be heatedmomentarily passes, and each commutator segment being of such a smallcircumferential length as to provide in parallel with the length of wirein engagement with its periphery a shunt resistance of value greatenough as to preclude sparking or arcing by shunt current flow ofmagnitude great enough to result in local formation of martensite in thesteel wire.

2. Apparatus according to claim 1, wherein in association with each setof commutator segments there is a plurality of brushes each having acircumferential width not exceeding the circumferential length of eachof the commutator segments, and the current supply path to each of theseveral brushes from the current source is of different electricalresistance such that the maximum electrical resistance is provided inthe current path to the brush which is circumferentially nearest to thepoint of initial engagement or disengagement of the wire from the rotarymember and is least in respect of the brush furthest from such point ofengagement or disengagement, so that the current flow between thecommutator segments and the wire surface is substantially uniform alongthe length of the wire.

3. Apparatus for effecting permanent elongation of martensitic formingsteel wire, so as to improve the creep resistance thereof, saidapparatus comprising a pair of rotary members each provided with aplurality of peripheral wire engaging grooves around which the wire isadapted to pass from one rotary member to the other, said grooves in thedirection of advancement of the wire being of progressively increasingdiameter up to a predetermined maximum diameter, so as to apply aprogressively increasing tension to the wire passing therearound, andbeing thereafter of progressively decreasing diameter in the directionof wire advancement, a third rotary member having a peripheral groovearound which the length of wire is adapted to pass from the last but onegroove of progressively increasing diameter to the groove of largestdiameter, means for supplying heating current to the length of wirepassing from between said two grooves last mentioned, said meanscomprising forming each of said two last mentioned grooves and thegroove of the third rotary member as a set of commutator segments spacedaround the circumference of the associated rotary member, withcircumferentially adjacent segments electrically insulated from oneanother, a current supply means associated with each set of commutatorsegments and comprising at least one current carrying brush, eacharranged to make contact with the commutator segments, atacircumferential position such that each segment which is in electricalcontact with a current carrying brush, is out of electrical contact withthat portion of the wire engaging periphery of the rotary member onto oroff which the length of wire to be heated momentarily passes, and eachcommutator segment being of such a small circumferential length as toprovide in parallel with the length of wire in engagement with itsperiphery a shunt resistance of value great enough as to precludesparking or arcing by shunt current flow of magnitude great enough toresult in local formation of martensite in the steel wire.

4. Apparatus according to claim 3, wherein in association with each setof commutator segments there is a plurality of brushes each having acircumferential width not exceeding the circumferential length of eachof the commutator segments, and the current supply path to each of theseveral brushes from the current source is of different electricalresistance such that the maximum electrical resistance is provided inthe current path to the brush which is circumferentially nearest to thepoint of initial engagement or disengagement of the wire from the rotarymember and is least in respect of the brush furthest from such point ofengagement or disengagement, so that the current flow between thecommutator segments and the wire surface is substantially uniform alongthe length of the wire.

5. Apparatus according to claim 1, comprises two rotary members eachprovided with a plurality of wire engaging grooves around which the wireis adapted to pass from one rotary member to the other, with the groovesbeing of progressively increasing diameter up to a predetermined maximumdiameter, so as to apply a progressively increasing tension to the wirepassing therearound, and being thereafter of progressively decreasingdiameter in the direction of wire advancement, a third rotary memberhaving a peripheral groove around which the length of wire to be heatedpasses from the last but one groove of progressively increasing diameterto the groove of largest diameter, said last mentioned two grooves beingprovided adjacent opposite ends of one of the said two rotary members,and being each constituted by one of said sets of commutator segments,and having in association therewith one or more current carryingbrushes, the third rotary member around which the length of wire to beheated passes being formed with a peripheral wire engaging grooveconstituted by a further set of commutator segments and having inassociation therewith one or more current carrying brushes, the arrangement being such that in the operation of the apparatus, the currentpasses between the third rotary member and each of the two commutatorsegments constituting the said two grooves of the one rotary member.

6. Apparatus according to claim 5, wherein the two rotary membersproviding the several wire engaging grooves of progressively increasingand progressively decreasing diameter are each mounted for rotationabout spaced parallel axes, characterized in that the third rotarymember around which passes the length of wire to be heated has its axisof rotation inclined to the mutually parallel axes of rotation of theother two rotary members, the arrangement being such that the plane ofrotation of the two grooves of largest but one and largest diameter atopposite ends of the one rotary member are each respectively aligned inthe position at which the length of wire respectively passes onto andoil? the third rotary member.

7. Apparatus according to claim 1, wherein the rotary members areprovided with wire engaging grooves of V form in cross section with thecircumferential length of the wireengaging part of each commutatorsegment being not more than six times the diameter of the wire to beelongated.

8. Apparatus according to claim 7, for use in improving the tensileproperties of martensitic steel wire in the form of helically :woundstrand or rope, wherein the circumferential length of the wire engagingpart of each commutator segment is not more than four times the diameterof the wire to be elongated.

9. Apparatus according to claim 7, for use in improving the tensileproperties of martensitic steel wire in the form of helically woundstrand or rope, wherein the circumferential length of the wire engagingpart of each commutator segment is not more than twice the diameter ofthe wire to be elongated.

References Cited UNITED STATES PATENTS 3,182,167 5/1965 McBrien 219-155X RICHARD M, WOOD, Primary Examiner.

'B. A. STEIN, Assistant Examiner.

1. APPARATUS FOR EFFECTIG PERMANENT ELONGATION OF MARTENSITIC FORMINGSTEEL WIRE, SO AS TO IMPROVE THE CREEP RESISTANCE THEREOF, SAIDAPPARATUS COMPRISING ROTARY MEANS ADAPTED TO APPLY TENSION TO A LENGTHOF WIRE PASSING OVER SAID ROTARY MEANS IN ENGAGEMENT THEREWITH, MEANSFOR SUPPLYING A HEATING CURRENT TO AND ALONG A PREDETERMINED LENGTH OFTHE WIRE WHICH IS UNDER TENSION, SO AS TO HEAT SUCH LENGTH TO ATEMPERATURE SUCH THAT AT THE TENSION APPLIED TO THE WIRE PERMANENTELONGATION THEREOF IS EFFECTED, SAID HEATING CURRENT SUPPLY MEANSCOMPRISING A ROTARY MEMBER HAVING A WIRE ENGAGING PERIPHERY FORMED AS ASET OF COMMUTATOR SEGMENTS SPACED AROUND THE CIRCUMFERENCE OF THEASSOCIATED ROTARY MEMBER, WITH CIRCUMFERENTIALLY ADJACENT SEGMENTSELECTRICALLY INSULATED FROM ONE ANOTHER, A CURRENT SUPPLY MEANSASSOCIATED WITH EACH SET OF COMMUTATOR SEGMENTS AND COMPRISING AT LEASTONE CURRENT CARRYING BRUSH, EACH ARRANGED TO MAKE CONTACT WITH THECOMMUTATOR SEGMENTS AT A CIRCUMFERENTIAL POSITION SUCH THAT